As described in Section REF , sources of systematic uncertainty include the choice of cutoff \(k_{\star }\) , the omission of tight-binding parameters in the minimal model, and the value of the interaction parameter \(\alpha _{\mathrm {g}}\) .
We have assumed the interaction parameter \(\alpha _{\mathrm {g}}\)  to be independent of layer number \(N\) , but it is anticipated that the effective strength of interactions could fall with \(N\)  due to screening [1]}, [2]}. This would lead to a further reduction in \(E_{\mathrm {g}}\)  and a fall in \(\Delta \)  for large \(N\)  in Fig. REF , say.
Additional tight-binding parameters such as \(\gamma _2\)  and \(\gamma _3\)  will introduce trigonal warping of the dispersion around each valley (so the Berry curvature, Fig. REF , will be anisotropic), and \(\gamma _4\)  will break particle-hole symmetry [3]}, [4]}; this is likely to reduce the value of the band gap. The additional tight-binding parameters are usually smaller in magnitude than the typical values of the band gap that we predict, but there is a possibility that additional parameters will change the qualitative nature of the ground state [5]}. However, even without these parameters, for our choice of cutoff and for \(\alpha _{\mathrm {g}} = 0.3\) , we find close agreement of band gap values in RMG with DFT calculations of Ref. [6]} (which considered \(N=3\)  to \(N=8\)  layers).
